Lightning Specification Meeting 2023/04/10

[t-bast]

The meeting will take place on Monday 2023/04/10 at 8pm UTC (5:30am Adelaide time) on Libera Chat IRC #lightning-dev. It is open to the public.

A video link is available for higher bandwidth communication: https://meet.jit.si/Lightning-Spec-Meeting

Recently Updated Proposals / Seeking Review

This section contains changes that have been opened or updated recently and need feedback from the meeting participants.

• Add compact-size fundamental type (Add CompactSize fundamental type #1062)
• Follow-up to Allow nodes to overshoot final htlc amount and expiry #1032 to fix onion errors (Update onion errors since we allow overpaying or under-CLTVing #1063)
• Question about Bolt11 descriptionHash (bolt11: drop requirement to check descriptionhash #1064)
• Onion messages BOLT 7: Onion message support (features 38/39) #759
• Offers Offers #798
• Add dust exposure threshold Add a max_dust_htlc_exposure_msat #919
• Taproot extension-bolt: simple taproot channels (feature 80/81) #995
• Taproot gossip extension-bolt: taproot gossip (features 32/33) #1059
• Dual funding interactive-tx: Add dual-funding flow, using the interactive tx protocol (feature 28/29) #851 (Store state when sending commitment_signed niftynei/lightning-rfc#13 and Use signed amounts in RBF messages niftynei/lightning-rfc#15)
• Splicing Splice draft (feature 62/63) #863
• Fat errors Attributable errors (feature 36/37) #1044
• Clarify channel_reestablish requirements Clarify channel_reestablish requirements #1049 or Rework channel_reestablish requirements #1051
• Peer storage backup Peer backup storage (feature 40/41/42/43) #881

Stale Proposals

This section contains pending changes that may not need feedback from the meeting participants, unless someone explicitly asks for it during the meeting. These changes are usually waiting for implementation work to happen to drive more feedback.

• Inbound fees Inbound routing fees blips#18 and Add a bLIP for backwards-compatible inbound fees blips#22
• Closing fee range turn-based protocol option_closing_rejected: turn-based fee_range coop close (feature 60/61) #1016
• Update static channel parameters zzz-extension-bolt: dynamic commitments #1026
• Liquidity ads option_will_fund: liquidity ads #878
• Sign commitments at various feerates Add option to sign commitments at various feerates (FEAT 32/33) #1036

Waiting for interop

This section contains changes that have been conceptually ACKed and are waiting for at least two implementations to fully interoperate.
They most likely don't need to be covered during the meeting, unless someone asks for updates.

• Don't force close until error is received after channel_reestablish Nodes shouldn't publish their commitment when receiving outdated channel_reestablish #934
• Websocket transport websocket address type: allow transport over RFC6455 #891

Long Term Updates

This section contains long-term changes that need review, but require a substantial implementation effort.

• Channel jamming draft: Staking Credentials token issuance/redemption #1043 draft: Upfront Fees to Mitigate Channel Jamming #1052
• Pinning attacks as related to splicing / dynamic commitments: https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-August/003665.html
• Quiescence BOLT 2: quiescence protocol (feature 34/35) option_quiesce #869
• Simplified commitment Feature 106/107: option_simplified_update. #867
• Hold htlcs before forwarding Add the ability to hold HTLCs before forwarding (FEAT 52/53) #989
• Trampoline routing Trampoline Routing (2021 edition) (Feature 56/57) #829 and Trampoline onion format (Feature 56/57) #836
• Anonymous gossip
• lnprototest (https://github.com/rustyrussell/lnprototest)

[t-bast]

I'll be a bit late to this meeting, I'll be in listening mode only for the first 15-20 minutes, but I'll be there afterwards!

[Roasbeef]

adding compact size:

• We did BigSize initially so we could avoid mixing little and big endian like Bitcoin does. BigSize is just the compact size, but big endian.
• Motivation was people wanting to store thing in the same format as does for Bitcoin consensus, instead of the raw elements.
  • Does anyone actually not deserialize again and just use it as a blob of bytes?

CLTV onion update:

• looks good, ACK'd by all

Description hash:

• People want to drop the requirement to check the description hash. As many times they don't actually even have the description itself. Also want to store MBs in the description or w/e.
• lnd open to modifying behavior of API to make the relationship clearer.
• General stance: don't change, people can fix their client libs.

onion messaging:

• small feedback, typos, etc
• also doing final pass over the test vectors as well -- should double check that correct
• route blinding in, use new message for route blinding to decrypt it, rebased on master

offers:

• rebased, adds some new fundamental types:
  • adds utf-8 string type
  • adds bip-340 type as well (schnorr signature)
• does this have a description hash?
  • doesn't inherit base5 stuff, so don't have that length limit

dust limit stuff:

• t-bast has reviewed, needs another person to sign off on

taproot:

• musig 1.0.0 -- libsecpzkp is fully caught up
• my goal (laolu): out of draft by EOW
• lnd progress:
  • PRs in lnd under active review, updated to use musig 1.0.0
• FROST stuff report from LDK:
  • can't use shachain in this setting, since want to split the preimage across many parties
  • could do MPC sha2, but then need something like spdz or w/e
  • potentially can try to arrive at new scheme that gives us the properties we need from shachain but uses asymmetric crypto?

taproot gossip:

• initial draft up now, people stating to dig into
• idea re modifications:
  • remove the requirement to give the taptweak, just have it be a taproot output?
    • shorter cut out instead of moving everything around into the node announcement, etc
  • go another step and add even looser coupling, and allow any value
    • a step towards letting basically any output at all be advertised

splicing:

• changing it to use delta amounts, so that means you need to use signed amounts
• so need to change one of the TLVs to also have an unsigned value
  • other thing that would start to intro would be inbound fee stuff

[carlaKC]

Finally catching up with transcripts (AI overlords briefly revolted).

Was this meeting recorded by any chance? If yes, could whoever has the video email it to me 🙏

[Roasbeef]

@carlaKC I think Elias was recording?

[tnull]

@carlaKC I think Elias was recording?

No, wasn't me unfortunately. Might have been @ellemouton as names are kinda similar (just a guess though)?